What is the best fixation target? The effect of target shape on stability of fixational eye movements

Thaler, Lore; Schütz, Alexander C.; Goodale, Melvyn A.; Gegenfurtner, Karl R.

Abstract

People can direct their gaze at a visual target for extended periods of time. Yet, even during fixation the eyes make small, involuntary movements (e.g. tremor, drift, and microsaccades). This can be a problem during experiments that require stable fixation. The shape of a fixation target can be easily manipulated in the context of many experimental paradigms. Thus, from a purely methodological point of view, it would be good to know if there was a particular shape of a fixation target that minimizes involuntary eye movements during fixation, because this shape could then be used in experiments that require stable fixation. Based on this methodological motivation, the current experiments tested if the shape of a fixation target can be used to reduce eye movements during fixation. In two separate experiments subjects directed their gaze at a fixation target for 17 s on each trial. The shape of the fixation target varied from trial to trial and was drawn from a set of seven shapes, the use of which has been frequently reported in the literature. To determine stability of fixation we computed spatial dispersion and microsaccade rate. We found that only a target shape which looks like a combination of bulls eye and cross hair resulted in combined low dispersion and microsaccade rate. We recommend the combination of bulls eye and cross hair as fixation target shape for experiments that require stable fixation.

Citation

Thaler, L., Schütz, A. C., Goodale, M. A., & Gegenfurtner, K. R. (2013). What is the best fixation target? The effect of target shape on stability of fixational eye movements. Vision Research, 76, 31-42. https://doi.org/10.1016/j.visres.2012.10.012

• Journal Article Type: Article
• Publication Date: Jan 14, 2013
• Deposit Date: Oct 23, 2012
• Publicly Available Date: Jan 26, 2015
• Journal: Vision Research
• Print ISSN: 0042-6989
• Publisher: Elsevier
• Peer Reviewed: Peer Reviewed
• Volume: 76
• Pages: 31-42
• DOI: https://doi.org/10.1016/j.visres.2012.10.012
• Keywords: Eye movements, Ocular fixation, Microsaccade, Drift, Dispersion, Slow control.
• Public URL: https://durham-repository.worktribe.com/output/1501922